Field Notes: Wrapping up Corn and Soybean Planting
Press Release
U of M Extension
Worthington, Minn. (05/20/2024) — After rain halted early planting progress, farmers are looking to wrap up the planting season. Drs. Jeff Coulter, Extension Corn Agronomist, and Seth Naeve, Extension Soybean Agronomist, discussed planting and replanting decisions on the May 15 Strategic Farming: Field Notes session.
Check corn stands: Corn populations down to 23,000 plants/ac can still result in a yield that is 92% of optimal. Ideally corn seedlings would be evenly spaced, but in reality, if spacing between plants is a bit uneven, this won’t have much of an effect on yield.
If you have corn to plant yet: Corn planted on May 20 and May 25 can be expected to yield 92 to 95% and 87 to 92% of corn planted in late April under ideal soil conditions, respectively.
Note if planting is delayed until May 22 to the 28, a hybrid 5 to 7 relative maturity units earlier than what is considered full season for the area would be recommended. Until this time, it is recommended to stay the course with original seed choices. If corn planting is delayed until May 29 to June 4, a hybrid 8 to 15 relative maturity units earlier than what is considered full season for the area would be recommended.
Check soybean stands: Critically assess a stand before deciding to tear it up and replant. A final soybean stand of about 100,000 plants per acre or less results in maximized yield. It is possible to interseed about 75,000 seeds per acre early in the season if stands are lower than optimal (e.g. around 50,000 to 75,000 plant per acre). Waiting a few days until both rows are combine ready at harvest should alleviate issues with maturity differences.
If you have soybeans to plant yet: Throughout late-April and May, there is a small but consistent drop in soybean yield, averaging about 0.1 to 0.2% per day as planting is delayed. Once we hit June, however, we can see a 1.0% to 1.25% drop in yield per day as planting is delayed.
Stay the course with your original soybean maturity until the second week of June. At that point a soybean variety 0.5 relative maturity units shorter than the original choice would be recommended. If planting is delayed until late June, it is recommended to plant a variety 1.0 relative maturity units shorter than what you’d normally plant.
Watch soil conditions at planting for both crops: If wet conditions persist, it becomes a balance between waiting for good soil conditions to plant, “mudding in” the crop, or if planting really gets delayed, taking prevent plant.
Soil conditions at planting can significantly impact yield potential of both corn and soybean. A rotary hoe can effectively help a crop struggling to emerge through a soil crust. In soybean, however, one must be very careful when seedlings are just starting to emerge (when you can see the hypocotyl arch) so plants are not broken off below the cotyledons, as this will kill the seedling.
Weigh the replant decision: Yield potential for an earlier planted field with reduced stands should be weighed against the yield potential of a later planted crop, along with the additional costs and time involved in replanting. Consider what herbicides and fertilizer that has been applied and that weed control can be a bigger challenge where stands are spotty and/or reduced. See z.umn.edu/crops for resources and further information on corn and soybean late planting and replanting decisions.
Listen to the podcast of this session at https://strategicfarming.transistor.fm/ .
Join us for University of Minnesota’s Strategic Farming: Field Notes webinar series, offered Wednesdays morning from 8 to 8:30 a.m. through August 21, for useful, timely and relevant research-based information on cropping issues throughout the growing season. For more information and to register, visit z.umn.edu/strategic-farming.
